At the university there, coin-sized disks are being produced from the cocoon of the tasar silkworm (Antheraea mylitta). According to Chinmoy Patra, an Indian scientist who now works in Engel’s laboratory, the fibre produced by the tasar silkworm displays several advantages over the other substances tested. “The surface has protein structures that facilitate the adhesion of heart muscle cells. It’s also coarser than other silk fibres.” This is the reason why the muscle cells grow well on it and can form a three-dimensional tissue structure. “The communication between the cells was intact and they beat synchronously over a period of 20 days, just like real heart muscle,” says Engel.

Despite these promising results, clinical application of the fibre is not currently on the agenda. “Unlike in our study, which we carried out using rat cells, the problem of obtaining sufficient human cardiac cells as starting material has not yet been solved,” says Engel. It is thought that the patient’s own stem cells could be used as starting material to avoid triggering an immune reaction. However, exactly how the conversion of the stem cells into cardiac muscle cells works remains a mystery.

Disks cut from the cocoon of the tasar silkworm grub provide a basic scaffold for heart muscle